Pushbutton mechanism



July v7, 1970 H. J. MAKwAY 3,519,166

A PUSHBUTTON MECHANISM Filed Feb. 25, 196e .4 sheetsfsheet 1 will( 2 #LH '3 i i AT-romuey `Iuly 7, 1970 l H. J. MAcKwAY 3,519,766

PUSHBUTTON MECHANISM Filed Feb. 23, 3.968r .4 Sheets-Sheet 5 6% 00000000 :w 00000000 2J 00000000 :im 00000000 soLsuom H4 i CoN'rllol. l I m ClfLculT' INVENTOL Y HArLoLn J. MAcKw/-w RTTOILHEY July 7 1970 H. J. MACKWAY 3,519,766

PUSHBUTTON MECHANISM Filed Feb. 23, 195e .4 sheets-sheet L INUD LEFLECTED LIQH T ABSOIZBIM LlbHT ILEFLECTIN LAYEFL INVEMTOYI HnrLnLo J. MAcKwAY ATTO 11H EY 3,519,766 PUSHBUTTON MECHANISM Harold J. Mackway, Haddon Heights, NJ., assigner to RCA Corporation, a corporation of Delaware Filed Feb. 23, 1968, Ser. No. 707,800 Int. Cl. H01h 9/26 U.S. Cl. 200-- 8 Claims ABSTRACT OF THE DISCLOSURE Pushbutton switches of the type in which, in each bank, the depression of one button releases a previously depressed button. A printed circuit board leading to the electrical contacts of one bank of switches acts also as a side wall for that bank of switches, and an electric and magnetic field shield member serves as its other side wall. Additional features of these switches include simple and inexpensive one-piece plungers, simple means for automatically illuminating the depressed buttons, simple means for atuomatically illuminating the depressed buttons, means for automatically electrically indicating whether a pushbutton in a bank is depressed, and means for resetting, in unison, a plurality of banks of switches.

BACKGROUND OF THE INVENTION Pushbutton switches are well-known and are commonly used for controlling the operation of electrical circuits. Typical of such switches are those illustrated, 'for example, in U.S. Pats. Nos. 2,414,307, 2,192,621 and 3,281,544, and many other patents in Class 200-5 and related classes. However, in one particular application, that of a matrix of such switches arranged in the forml of a keyboard and employed for the purpose of entering binary information into a data processing machine, the known switches have been found not to be entirely satisfactory.

For example, one commercially available switch is guaranteed for 100,000 operations, whereas in the particular requirement mentioned above, at least a million operations should be performed during the life of the switch. A second disadvantage of the known switches resides in their complexitya factor which accounts yfor their high initial cost and their potential high cost for maintenance. IFinally, in the known switches, features such as switch rbutton illumination, switch reset capability and others, either are completely unavailable or are of excessive cost.

The object of this invention is to provide a greatly im'- proved switch of good operating characteristics, of extremely long life and relatively low cost.

SUMMARY OF THE INVENTION In the pushbutton type switch bank of the present invention, each plunger element is formed of a single sheet of metal and is formed with a first cam surface at one edge thereof which, when the plunger is depressed, engages a latch and causes it to release any other plunger which previously may have been depressed and a second cam surface at the opposite edge thereof lfor engaging one of a group of side-by-side elements which prevent the depression of any other plunger. The two cam surfaces of said plunger, in a preferred form of the invention, together define the pointed end of said plunger.

The side-by-side elements mentioned above are normally biased to a home position when none of the plungers is depressed. According to a feature of the invention, means coupled to an end of one of the elements actuates a switch which is common to all plungers, when any one of the elements is moved in response to the depression of a plunger.

Another 'feature of the invention is the use of a printed United States Patent O 3,519,766 Patented July 7, 1970 circuit board to mount the switches actuated by the plungers, to carry the printed wiring for said switches, and to serve as a side wall of the housing for a bank of the switches. A second side wall serves as an electric and magnetic field shield and prevents the operation of any switch bank from adversely affecting the operation of any other switch bank.

A fourth feature of the invention is the use of transparent pushbuttons movably mounted in guide channels and formed with internal prism surfaces. The guide channels are formed with coatings optically coupled through the side walls of the pushbuttons of these prism surfaces so that in one position of the pushbutton, the face of the pushbutton is dark and in another position of the pushbutton, its face appears to be lit up.

A iinal feature of the switch bank of the invention is its ability automatically to be reset. Reset means are coupled to the latches of all switches and in response to an BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a plan view, with one side wall removed, of a switch bank according to the invention;

FIG. 2 is a section taken along line 2-2 of FIG. 1;

FIGS. 3-4 are plan and edge views of the plunger assembly of the switch of FIG. 1;

FIG. 5 shows one side wall of the switch of FIG. l;

FIG. 6 is a section taken along line 6 6 of FIG. 5;

FIG. 7 is a plan view of the switch of FIG. 1 which shows the back side of the printed circuit board of FIG. 5;

FIG. 8 is a top view of a keyboard consisting of `6 banks of switches arranged side-by-side and showing the means for resetting all banks in unison;

FIG. 9 is an end view of 5 banks of switches side-byside; and

FIG. l0 is a perspective, partially broken-away View of a portion of FIG. 9.

DETAILED DESCRIPTION The switch bank shown in FIGS. l and 2 includes a housing 10 formed of a plastic material such as a polycarbonate. (One suitable commercially available plastic is Lexan made by General Electric.) This housing includes end walls 12 and 1.4 and a top wall 16, these three walls being formed of a single piece of material. The second part 17 of the housing 10 serves as a guide for the pushbutton plungers. It is formed with ten slots through which the ten plungers 26 fit. A third part 18 of the housing serves as a guide for the polycarbonate plastic wedge-shaped elements, 22a, 22b 22j. The polycarbonate plastic parts 17 and 18 are secured to the end walls 12 and 14 by two metal screws 20.

Located within the housing are ten plungers 26a, 26h 26j. The shaft 27 of each plunger passes through a slot 24 in the upper wall 16 and the opposite end of each plunger passes through a slot 25 in the part 17 at the lower part of the housing. These two slots therefore permit the plunger to move only along a straight line path.

Each plunger is normally maintained in its retracted position by means of a coil spring, one of which is shown at 28. The coil spring is secured at one end to the upper wall 16 of the housing and at its other end to a tab 30 on the body of the plunger. The plunger is made of a nonmagnetic metal such as brass and is stamped out in a single operation. This stamping process both produces a plunger of the shape shown with the tab 30 bent in the manner shown.

A transparent pushbutton of molded acrylic plastic, such as Plexiglas, one of which is shown at 32, is located at the end of each plunger. The details of this pushbutton are shown more clearly in FIG. 3. The lower surface is cut in inverted V-shape to provide two prism surfaces 34 and 36. For the sake of convenience, each prism is at an angle of 45 and the angle between the two surfaces 34 and 36 is 90.

FIG. 3 shows that the upper part 38 of each pushbutton is somewhat thicker than the lower part 40 of the pushbutton. The reason for this will be discussed shortly.

The plunger body is pointed at its end. The two surfaces 42 and 44 act as cam surfaces when the plunger is depressed. As will be discussed in more detail shortly, cam surface 42 pushes a latch mechanism 68 (FIG. 1) in one direction to effect the release of any other pushbutton which may then be in a depressed condition, and the surface 44 engages a wedge and pushes it in the opposite direction. In brief, the purpose of doing this is to prevent a second pushbutton from becoming latched and also to actuate the switches 56 and 58. The slot 46 is for the purpose of engaging the latch mechanism so that when the plunger is depressed, it will remain depressed and not be pulled back by a spring (28, FIG. l).

There is secured to the side of the plunger, a ceramic permanent magnet 48. Its purpose is to control the operation of a reed-type switch 50, such as shown in FIG. 6. The contacts of the switch are normally biased to the open position by the natural tension of the switch elements 52 and 54. When a pushbutton is in its released position, as shown in FIG. 2, the pole of the permanent magnet 48 is located adjacent to the Contact region and the contacts remain open. However, when a pushbutton is depressed so that the center of the magnet is aligned with the contact area, as shown in FIG. 6, the switch contacts 52-54 close. The theory is well understood and need not be discussed here and the switches 50 are commercially available.

Returning to FIG. l, there is secured to the channel element 18, two microswitches 56 and 58. The arms (actually leaf springs) 60 and 62 for these microswitches are engageable by a bent element 64 formed of spring steel wire, which is secured at one end to the end wedge 22a. The center region 64a of the spring element 64 rides in a channel in the plastic supporting bracket 66 of the microswitches.

The polycarbonate plastic latch mechanism for the plungers is element 68. It is slidable in the direction of arrows 70 but is normally maintained in the position shown in FIG. 1 by means of the leaf spring 72 at the extreme right end of the channel 18, as seen in FIG. l.

In the operation of the switch bank of FIG. 1, assume first that all plungers are retracted. The leaf springs 60, 62 move the wedge 22a to the right via the bent element 64 and the microswitches 60, 62 are open.

Assume now that the plunger 26a is in its depressed state, as shown, and that all of the other plungers are in their upper or retracted position. When the plunger 26a is depressed, the wedge-shaped element 22a is moved to the left and this moves with it, the bent element 64. The latter actuates the microswitches 56 and 58 and they indicate to a computer that a plunger in the bank shown is depressed. It is important, for reasons not necessary to discuss here, that the computer have this information.

Assume now that it is desired to depress plunger 26b. As the plunger moves down, the cam surface 42 at the end of the plunger rides against the latch mechanism 68 and moves this mechanism to the right. Concurrently, the cam surface 44 engages the wedge 22b and moves it to the left. After the plunger is depressed a certain amount, the latch mechanism 68 moves sufficiently so that it disengages from the slot 46 of the depressed plunger 26a, releasing plunger 26a. The spring (not shown) of plunger 26a now withdraws this plunger to its retracted or upper position.

The plunger 26b continues to move down and shortly its notch 46 aligns with the latch 68 and the spring 72 thereupon snaps the latch into position to hold the plunger 26b in its depressed position. At the same time, the wedge-shaped element 22b has moved to the left until it engages the lower part of the Wedge-shaped element 22a. Thus, the wedge-shaped element 22a is returned to the position shown and the microswitches 56 and S8 return to their actuated position. Note that when a plunger is released, the switches 56 and 58 also momentarily are released before the plunger then being depressed is latched.

Finally, in the extreme down position of the plunger 56h, all of the wedges are so positioned that insufficient space remains to permit a second plunger to be fully depressed While the plunger 26b is being maintained in the depressed position, If the plunger 26b is being maintained fully down with one finger, no other one of the plungers can be pushed to its fully depressed position as, before it gets there, one of its cam surfaces 42 or 44 will engage one of the wedges 22. Those plungers 26e-26]' to the right of plunger 26b will engage a wedge-shaped element with their cam surface 44. If, on the other hand, it were attempted to depress plunger 26a while plunger 26b was maintained fully depressed, its cam surface 42 would engage wedge-shaped element 22b which would prevent plunger 26a from being fully depressed.

The side walls and 82 of the switch bank of FIG. 2 also have important functions in addition to the usual one of environmental protection. The side wall 80, for example, serves as a printed circuit board. The reed-type switch elements 50 are fixed to the inner surface of this circuit board 80 and printed circuit wiring, as shown in FIG. 7, is located on the outer surface of the circuit board 80. The generally circular areas shown in FIG. 7 are the points at which the leads for the reed switches 50 are located as shown somewhat more clearly in FIG. 2. After the printed circuits are laid down, they are insulated by a transparent material in a manner well understood in the art.

The side wall 82 is formed of a magnetic material such as iron and its purpose is to provide electrical and magnetic isolation between successive bangs of pushbutton switches. Such successive banks are shown in end view in FIG. 9. Note that the shield 82 for switch bank 90, for example, is located immediately adjacent the printed circuit board 80 for switch bank 92. Thus, any electrical or magnetic fields present in switch bank 92 are shielded from switch bank 90. In a similar manner, the shield 82 for switch bank 92 isolates it from the switch bank 94 and so on.

The design of the pushbuttons is such that they are self-illuminating without the use of any external power. As is shown in FIG. 9, incident light passes through the upper face `96 of each button 32 and is then reflected from the prism surfaces 34 and 36 to the walls of the U-shaped housing 98. As is seen more clearly in FIG. l0, the upper part 100 of each `wall of the housing is coated with a light-absorbing layer such as dull black paint, whereas, the lower part 102 of each side wall is covered with a light-reflecting layer. As one example, the coating may be a masking tape such as Scotchcal in a yelloworange or similar fluorescent, very-bright shade. These light-absorbing and light-reflecting layers are located in the same position both on the inner and the outer surfaces of the walls of each U-shaped housing for reasons which will become clear shortly.

In the operation of the arrangement shown in FIG. 9, when a pushbutton such as 32a is in the upper position, incident light passes through the pushbutton and is refiected from the prism surfaces 34 and 36 onto the lightabsorbing layer 100. This light is very poorly reflected `from layer 100 so that the button looks very dark to the eye. On the other hand, when a button such as 32C is depressed, fthe incident light strikes the lower region 102 of the outside surfaces of the two adjacent U-shaped channels 9812 and 98C. This light is reflected back from the prism surfaces of button 32C and through the upper surface of the button 32C to the eye. To the viewer therefore, the depressed switch looks bright and appears to emit colored light, the color depending upon the material of which the layer 102 is made.

The fact that the U-shaped housings 98 are coated with light-absorbing and light-emitting layers on their inner and outer surfaces permits a saving in costs. One such housing is needed for only every other switch bank so that if there is an add number n of side-by-side banks only (n-i-iU/Z housings 98 are needed.

When a pushbutton is depressed, its surfaces 38 actually engage either the outer or the inner surfaces of a U-shaped housing 98. However, the recessed portions 40 of the switch do not make such contact. Thus, the recessing prevents abrasion of either surface -40 and this is important as such abrasion would soon cause these surfaces to become translucent rather than transparent and the self-illuminating properties of the button to become lost.

It is sometimes desirable, upon command from the computer, to reset all banks of a switch matrix in unison. The resetting of all switches, in accordance with the invention, is accomplished by using a pair of solenoids 110 and 112 positioned in the manner shown in FIG. 8. These solenoids are mechanically coupled by linkages 114 and 116 to a bar 118 which is engaged with the extending ends of all of the latches 68. (In FIG. l, this end of latch 68 is visible at the lower left.) When both solenoids are energized by the solenoid control circuit 120, the bar 118 is retracted and this causes all of the latch mechanisms to move in a direction to release the plungers of all switch banks.

While for purposes of illustration, FIG. 8 shows a pushbutton with 6 switch banks, each with 8 switches, it is to be appreciated that, in practice, the pushbutton may be much larger than this. Similarly, while the switch bank of FIG. 1 is shown to have one magnet and one switch per plunger, in practice, there may be more magnets and switches per plunger. For example, there may be magnets glued to each surface of the plunger and a switch adjacent each magnet so that the depression of a plunger simultaneously will actuate several switches. As a matter of fact, models have been constructed where as many as five switches have been actuated by a single plunger.

As stated in the introduction, the best commercially available switch of the general type discussed herein is guaranteed for only 100,000 operations. Extensive tests have been performed of switch banks made according to the present invention and all such banks have gone better than one million operations without failure. A number of such banks already have exceeded two million operations and some, it is believed, will go well in excess of three million operations. With respect to costs, it is possible to manufacture a switch bank of the present invention for less than one-half the price of competitive designs. The reason is the very simple nature of the various parts. As already mentioned, the metal plunger is punched from a single piece of metal in a single operation. The plastic parts of the housing are molded in three pieces; one piece for element 12, 14, 16, one piece for element 17 and one piece for channel 18. The latch is molded as a fourth piece. The side walls serve multiple purposes, one including that of a printed circuit board and the other including that of a magnetic and electrical iield shield. In addition to all of this, each switch bank has such additional important features as self-illumination of pushbuttons, automatic reset capability, and means for indicating whether or not a pushbutton is depressed.

What is claimed is:

1. In a pushbutton switch bank of the type including a latch and a plurality of plungers, and in which the depression of one plunger actuates the latch to cause it to release any other plunger engaged thereby, and also including a plurality of elements responsive to the depression of one plunger for preventing the depression of any other plunger, the improvement in each plunger comprismg:

solely a single generally flat member formed from a single sheet of material and formed with a first cam surface at one edge thereof, which when the plunger is depressed, engages said latch and causes it to release any other plunger which previously may have been depressed, and a second cam surface at the opposite edge thereof for engaging one of said elements when said plunger is depressed, and formed also with a slot along one of said edges for engaging said latch.

2. In a switch bank as set forth in claim 1, said two cam surfaces on said improved plunger comprising two edges of said plunger which together dene the pointed end of said plunger.

3. In a pushbutton switch bank as set forth in claim 1 in which said plungers are located in a housing, further including switch means fixed to said housing, and a switch engaging means coupled to an end one of said plurality of elements for actuating said switch means in response t0 the depression of any one of said plungers.

4. In a pushbutton switch bank of the type including a latch and a plurality of plungers, and in which the de pression of one plunger actuates the latch to cause it to release any other plunger engaged thereby, and also including a plurality of elements responsive to the depression of one plunger for preventing the depression of any other plunger, an improved plunger comprising:

a member formed from a single sheet of material and formed with a first cam surface for engaging and moving said latch in one direction for causing it to release any previously engaged plunger, and a second cam surface for engaging and moving one of said elements and for moving others, if any, adjacent to said one element, in the direction opposite from the direction of movement of said latch, said two cam surfaces together defining the pointed end of said plunger.

A pushbutton type switch bank comprising, in combination:

a channel;

a plurality of elements, movable relative to one another, each formed with at least one cam surface adapted to be engaged by the end of a plunger, said elements for preventing more than one plunger from being depressed at a time, each element having a length which is a'fraction of that of said channel, said elements being arranged one after another, in end-toend abutting relation, along the length of said control;

biasing means at one end of said channel for normally biasing said elements for maintaining all elements in a home position when none of said plungers is depressed;

a switch; and

means coupled to the end one of said elements which moves in response to the displacement of any one of said elements from its home position, for actuating said switch.

6. In a pushbutton type switch bank as set forth in claim 5, said last-named means including said biasing means.

7. In a pushbutton switch bank as set forth in claim 1, said plungers being located in a housing, each said plunger being formed with a tab along one edge thereof for anchoring a spring, and further including for each plunger a spring secured between said tab and a point on said housing such that each spring tends to oppose the depression of its plunger.

8. A pushbutton type switch matrix comprising the combination of:

a plurality of switch banks arranged side-by-side so 7 that the pushbuttons form a keyboard array, each switch bank comprising:

a latch; a plurality of plungers, each plunger actuated by a pushbutton, each plunger for actuating said latch and causing it to retain said plunger in a depressed position in response to the depression of said plunger and release means for said latch extending from said bank for causing the latch to release any plunger it may be retaining, when said release means is actuated; and a common release mechanism for all of said latches comprising means mechanically coupled to all of said References Cited UNITED STATES PATENTS Thompson. Lewandowski. Mathes.

Hutt. Woodward. Wirsching.

release means for concurrently actuating the re 15 20o-153, 169

lease means for all latches.

U.S. C1. X.R. 

